DragWindowPosition Doesn't Work

My DragWindowPosition doesn't work. I was watching a tutorial: https://www.youtube.com/watch?v=W68rCj6baRk and it worked up until when I added the DragWindowPosition. When I played my game, the window was draggable but my Inventory buttons and Close button disappeared. It think this is a problem with the position or size of my GUI but I don't know how to fix it. My script:

START:

 #pragma strict
 //Private Variables
 private var InventoryOn = false;
 private var scrollBarChopGrid : Vector2 = Vector2.zero;
 private var GridValue : float = -1;
  
 //GUI Pos/Size
 var NamePosition : Vector2 = new Vector2(30,30);
 var NameSize : Vector2 = new Vector2(250,250);
 var GridPosition : Vector2 = new Vector2(10,5);
 var GridSize : Vector2 = new Vector2(323,410);
 var ClosePosition : Vector2 = new Vector2(312,5);
 var CloseSize : Vector2 = new Vector2(35,35);
 var ScrollPosition : Vector2 = new Vector2(0,95);
 var ScrollSize : Vector2 = new Vector2(355,500);
 var WindowPosition : Vector2 = new Vector2(0,0);
 var WindowSize : Vector2 = new Vector2(360,360);
 var DragWindowPosition : Rect = Rect(0,0,WindowSize.x,WindowSize.y);
  
 //Textures
 var InventoryWindow : Texture;
 var CloseIcon : Texture;
 var Grids : Texture [];
  
 function Update () 
 {
    //On or Off
    if (Input.GetKeyUp ("i"))
    {
  
       if (InventoryOn == false)
       {
          InventoryOn = true;
       }
       else if (InventoryOn == true)
       {
          InventoryOn = false;
          scrollBarChopGrid.y = 0;
       }
    }
    //Window Drag Fix
    if (Input.GetKeyDown("left shift"))
    {
       if (Input.GetKeyDown("i"))
       {
          DragWindowPosition.x = 10;
          DragWindowPosition.y = 10;
  
       }
    }
 }
  
 function OnGUI()
 {
    if (InventoryOn ==true)
    {
       DragWindowPosition = GUI.Window(0, DragWindowPosition, DoMyWindow, "");
    }
 }
  
 function DoMyWindow(WindowID : int)
 {
    if (InventoryOn == true)
    {
       GUI.BeginGroup(new Rect(WindowPosition.x, WindowPosition.y, WindowSize.x, WindowSize.y), InventoryWindow);
       //Name
       GUI.Label(Rect(NamePosition.x, NamePosition.y, NameSize.x, NameSize.y), "Your Inventory");
  
          //Close Button
          if (GUI.Button(Rect(ClosePosition.x, ClosePosition.y, CloseSize .x, CloseSize .y), CloseIcon))
          {
             InventoryOn = false;
          }
          //Scroll Bar
          scrollBarChopGrid = GUI.BeginScrollView(Rect (ScrollPosition.x, ScrollPosition.y, ScrollSize.x, ScrollSize.y), scrollBarChopGrid, Rect(0,0,0,420));
             //Grid
             GridValue = GUI.SelectionGrid(Rect(GridPosition.x, GridPosition.y, GridSize.x, GridSize.y), GridValue, Grids, 5);
          GUI.EndScrollView();
  
          //Dragable Window
          GUI.DragWindow (Rect (WindowPosition.x, WindowPosition.y, 10000, 40));
       GUI.EndGroup();
    }
 }

END

Another thing wrong with the Inventory is that my Inventory Buttons go underneath the texture of the Inventory halfway through. This problem is only fixable, though, if I fix the first problem with the DragWindowPosition. I tried to explain this the best way I could but if you have any questions then please ask.